Recently, a variety of synthetic resin materials have been used for production of housings and parts for OA devices and home appliances, connectors, auto parts, construction materials, household articles, fiber products and others. However, synthetic resin materials, which are inflammable, often need to have flame retardancy for assurance of fire safety, especially when used as home appliances, electric/electronic parts, and OA-related parts, and blending of various flame retardants is under study for that purpose.
A method of using a halogen-based flame retardant such as brominated polystyrene and an antimony-based flame retardant such as antimony trioxide in combination is known as the method to make a resin flameproofed, but such a flame retardant may generate toxic gas on combustion, and thus regulations on resin compositions containing halogen-based flame retardants got severer than before. For that reason, developments for non-halogen flame retardants are intensively in progress.
Methods of making a resin composition flameproofed without using a halogen-based flame retardant include, for example, those by using a metal hydroxide and by using a phosphorus compound. In the case of the method of using a metal hydroxide, it is possible to obtain desired flame retardancy only by using it in a large amount, but use of it in a large amount unfavorably causes a problem of deterioration of the properties inherent to the resin.
Methods of using an organic (condensed) phosphate ester compound and also by using red phosphorus were known as the methods of making a resin flameproofed by using a phosphorus compound. Relatively low-molecular-weight organic (condensed) phosphate esters are unsatisfactory from the points of volatility, sublimability, and heat resistance and have a problem that the flame retardants bleed out when the resin composition containing the same is used at high temperature for an extended period of time. Red phosphorus causes a problem that toxic phosphine gas is generated during drying and molding of the resin composition.
In addition, in the case of high-heat-resistance nylon resins demanding a processing temperature of 300° C. or higher, there is currently no phosphorus-based flame retardant that can withstand the processing temperature, and metal salts of dialkylphosphinic acid, only flame retardants that are considered sufficiently heat-resistant, had a problem that they cause corrosion of the metal regions of the extruders and injection molding machines such as cylinders and screws. Further, high-heat-resistance nylon resin compositions should be superior in heat resistance on reflow process, for example when used in connector application, but there is still no non-halogen flame retardant that has sufficient heat resistance on reflow process.
Patent Document 1 discloses a method of producing a flame-retardant triallyl isocyanurate prepolymer, characterized in that, in preparation of the prepolymer by polymerization of triallyl isocyanurate, as a controlling agent of polymerization, 6H-dibenz[c,e]-[1,2]-oxaphosphorin (molecular weight: 216.17) is added together with a polymerization initiator to the triallyl isocyanurate in an amount of 1 to 200% by weight.
Alternatively, Patent Document 2 describes a composition comprising a phosphorus-containing compound having a particular structure and an amorphous resin, which is improved in bleed-out resistance, but deterioration of the bleed-out resistance and the physical properties thereof under high-humidity high-heat condition is yet to be improved.